Organotypic cultures of mammalian nerve tissues will continue to be used to study problems related to myelinogenesis, synaptogenesis and the maintenance of the developed state. The effects of various manipulations of the tissues' environment, which will include metabolic and other toxins, antimetabolites, antibodies, etc., will be examined by light and electron microscopy, microelectrode recordings of bioelectric activities and chemical determinations of enzymes and substrates to document any resultant changes. Bibliographic references: Kristensson, K., Sheppard, R.D. and Bornstein, M.B.: Observations on uptake of herpes simplex virus in organized cultures of mammalian nervous tissue. Acta. Neuropath. 28;37-44, 1974; Kristensson, K. and Bornstein, M.B.: Effects of iron- containing substances on nervous tissue in vitro. Acta Neuropath. (Berl.) 28, 281-292 (1974).